Clock with digital display

ABSTRACT

A digital display timepiece having a panel of display elements which change their optical properties when electrically excited, an electronic circuit, the outputs of which are connected to the display elements, and a time base controlling the logic circuit, such that excitation of various sub-assemblies of said display elements controlled by the logic circuit displays the desired time, where the logic circuit and the display panel are so connected as to constitute a monolithic unit having a minimum number of input connections linking the output of the time base to the logic circuit.

United States Patent Girard 51 Sept. 19,1972

[ 4] CLOCK WITH DIGITAL DISPLAY 3,508,391 3! 1970 Lee ..58I23 R (72] Inventor; Hem Gin! is 3,541,799 11/1970 Langley .5812! R 3.466.498 9/1969 De Koster et al. .5850 R 1 Asslgnw a ac r de M ti- Rolex 3.509.715 5/ 1970 De Koster et al. ..58l50 R S.A., Canton of Bern, Switzerland 22 med: 0. 16 I 70 Primary Examiner-Richard B. Wilkinson l 9 Assistant Examiner-Edith C. Simmons .lackmon 1 PP 31,283 Attorney-Stevens, Davis, Miller & Mosher 301 Foreign Application Priority om [571 ABSTRACT 0 t 2| 1969 A digital display timepiece having a panel of display c Swmefland 5727/69 elements which'change their optical properties when 52 electrically excited, an electronic circuit, the outputs 1 58/50 58/23 ii of which are connected to the display elements, and a [5'] lat. CL 3100 G04) 37/00 G04, 19/30 time base controlling the logic circuit, such that ex- [58] dd 0 sank 58,23 BA so citation of various sub-assemblies of said display elemeats controlled by the logic circuit displays the desired time, wherethe logic circuit and the display [56] References cm panel are so connected as to constitute a monolithic V unit having a minimum number of input connections UNIT 51 1153 PATENTS linking the output of the time base to the logic circuit. 3,505,804 4/ 1970 Hofstein ......58l50 5 Claims, 3 Drawing Figures PA'TEN'TEDSEP 19 me SHEET 2 BF 2 H H01 Am CLOCK WITH DIGITAL DISPLAY The present invention concerns a clock with digital display composed of a visible panel provided with display cells, each one of which is formed of a group of fixed display elements which are capable of changing their optical properties when excited by an electrical pulse, an electronic logic circuit, the outputs of which are connected to the display elements in order to transmit these pulses to them, a time base controlling the electronic logic circuit, and a power source, all being arranged in such a manner that at each moment the indication of the time formed by the cells occurs as a result of the excitation of various sub-assemblies of their elements.

Clocks have already been designed which correspond to this definition. In these clocks each one of the display cells were composed of a certain number of electric lamps or luminous elements distributed inside of a definite area so as to be able to form the various numbers indicating the time, for example the six numbers indicating the hours, minutes and seconds. The lamps were turned on and off by means of a device controlled by pulses provided by the time base. These clocks were relatively large in size, however, and the device for decoding the control pulses, in certain cases an electromechanical device, occupied a large space inside the case of the clock.

If it is desired to reduce the size of such clocks and make them independent, assuring their operation from a power source placed inside of the case itself, for example a miniature battery, the circuits of the decoding device should be designed in such a way as to prevent any loss of power. If it is furthermore desired to mass produce these clocks then the manufacturing of the display cells and their connection to the decoding circuits also present difficulties.

The purpose of the present invention is to create a clock with digital display of the type mentioned above which can be constructed in the size of a small clock, that is to say having dimensions not very much larger than a wrist watch while assuring the reliability of the various components and current consumption which is as low as possible. In particular, the invention concerns the creation of a monolithic panel of small thickness provided with hybrid circuits mounted in an unmovable fashion in the clock of which the panel comprises the dial.

With this purpose in mind, the clock according to the invention is characterized by the fact that at least a part of the electronic logic is connected to the panel so that the latter comprises a monolithic unit equipped with the display elements and a minimum number of input connections connecting the output of the time base to the electronic logic circuit built into the panel, the latter being attached in a detachable fashion in the timepiece.

The attached drawing represents, by way of example and schematically, the essential elements of two forms of design of the item according to the invention.

FIG. I is a top view of the display panel in the first form of design.

FIG. 2 is a partial and schematic view of the dial of the clock in FIG. 1, and

FIG. 3 is a simplified block diagram of the second form of design of the invention.

FIG. 1 shows essentially the arrangement and shape of the display cells I to 13 imbedded in a panel which forms the dial of a clock according to the invention. These cells are intended for representing the letters and numbers of a complete time indication including not only the hours, the minutes and the seconds, but also the day of the week and the date, as well as an additional permanent indication. These cells are of three different kinds: The cells 1 to 8 represent numbers, the cells 9 to 12 represent letters indicating the day of the week and the month and the cells 13 can be grouped into a single one giving a permanent indication, for example an indication of the brand.

In each cell the display elements 14 are used to form the desired indications. As can be seen from the draw ing, they present an elongated surface extension: These are rectangles, trapezoids or other types of two-dimensional geometric figures, the length of which is greater than the width. Each one of the cells 1 to 8 have seven elements 14, whereas the cells 9 to 12 have 14 each. It is easy to understand that by altering the optical properties of certain display elements in each cell so as to distinguish these elements from the background in which they are normally imbedded and unnoticed it is possible to inscribe a complete time indication in the dial of the clock. It is only necessary that each element of display 14 be connected by a connection 15 to an appropriate electronic logic circuit which itself is fed by input pulses supplied by a time base with a frequency divider in order for the time indication to be permanently provided. With the aid of the cells 13 the permanent indication which is to appear on the display panel, for example the brand, appears in a form exactly the same as that of the rest of the time indication.

At the present time it is possible to design cells such as cells 1 to 13 having dimensions which are extremely small, in particular the thickness, and a sufficiently low power consumption for all of these cells to be able to be powered by miniature batteries. Thus, the cells 1 to 13 can include the following parts: The upper section of the cell can be formed by a transparent conducting plate constituting an electrode and placed under a protective glass, this glass covering the entire clock. An active medium is placed between the transparent conducting plate and the bottom of the cell. This medium can be of a diverse nature. The bottom of the cell then comprises the display elements 14 distributed as shown in FIG. 1 according to the type of cells. Since the transparent conducting plates of each cell are joined together and connected, for example by pin 16, to one of the poles of the electronic logic circuit, it can be seen that if a display element 14 is subjected to a surge of current then an electrical field will be created through the active medium mentioned above.

This active medium may itself be of a different nature according to the forms of design. It could be, for example, a solid layer of a preparation having a phosphorus base, insulated from the conducting display elements 14, the latter being made, for example, of aluminum and insulated from one another. With an active medium of this kind when the pulse subjected to a display element has sufficient current the element becomes luminescent. However, there can also be provided between the transparent electrode and the conducting display elements an active medium which is composed of a liquid having a crystalline structure which is normally transparent but which becomes opaque when it is subjected to a difference in potential. It then becomes conducting so that the current passes through it. Active mediums of this kind have already been known for a long time. They are used particularly in sound cinematography. Under the effect of the passage of the current they assume a more or less dark gray color. It suffices, therefore, to arrange the bottom of the cells and the display elements 14 so that they diffuse as perfectly as possible the ambient light and assume therefore a white appearance so that the time indications can be inscribed in gray on the white background of the cells as soon as they are exposed to the light. The advantage of a design of this kind is that the difference in voltage which must prevail between the electrodes situated on both sides of the active medium is relatively small. A voltage of several volts is adequate to render visible the signs of a cell of for example 3 X 7 mm. In a timepiece of the size of a wrist watch the surface dimensions of the numbers and letters of a time indication can be relatively small. It then becomes possible to reduce the thickness of the active medium and consequently reduce the voltage of the pulses provided to the cells.

FIG. 2 shows schematically a view following the longitudinal axis of the cell 1 through the panel of FIG. 1. There can be seen a part of the elongated segments 14 immersed in a covering 33 made of insulating material of the same appearance as the segments. In the form of design shown here the segments 14 are electroluminescent diodes. Bach diode is provided with a connecting pin and the cell is disposed in a recess made in the thickness of the support 30 of insulating material which forms the frame of the dial of the timepiece described. The plate 30 in which all of the cells 1 to 13 are imbedded is covered by a transparent sheet 31. The inside of the sheet 31 is also treated so as to become conductive and to connect one of the poles of each one of the segments 14 to the connecting rod 16 which is imbedded in the panel 30 and which is connected electrically to the conducting layer covering the lower side of the sheet 31. This connecting plug 16 protrudes behind the panel. As regards the pins 15 of the various segments 14, they are connected by thin wires 29 to the integrated circuit 28 which contains the electronic components which are needed to assure the excitation of the segments to form the indication which is to be made by the cell. The integrated circuit 28 is attached to the other side of the panel 30 and is imbedded, as are the wires 29, in an insulating protective layer 32.

The electronic logic circuit provided for controlling the cells 1 to 12 can include nine circuits such as the element 28 attached to the other side of the panel 30. in effect, it will be necessary to have one decoding circuit for each one of the cells 1 to 6, but one circuit can be used for each one of the pairs of cells 9 10, 7 8 and 11 12. These various integrated circuits are connected to one another by connections such as the connection 34 and each integrated circuit can include a frequency divider so that it will only be necessary to equip the panel described with an input plug similar to the plug 16 which is intended for receiving the signal coming from the time base and with a third plug for the feed. The panel will thus constitute a monolithic unit provided with a minimum number of connections and can be attached removably to the inside of the wall of the timepiece described. It will be the timepieces dial provided with all of the elements necessary for displaying the time. When the panel is attached to the structural elements of the timepiece the connecting rods which protrude on the other side of it, such as the com nections l6, catch onto corresponding connecting plugs connected to the other active elements of the timepiece. In some cases the number of input connections of the panel can be greater than three, particularly when additional elements are provided for adjusting the hour, date, day or month.

The circuits are arranged in such a way that the circuit connected to cell 6 receives a pulse every second, the circuit allocated to cell 5 receives a pulse every 10 seconds and so forth right up to cell 1, the decoding circuit of which receives a pulse every ten hours. The decoding circuits of the pairs of cells 9 l0 and 7 8 receive a pulse every day and that of the pair of cells I l 12 receives a pulse each month. The decoding circuits assure at all times the formation of the time indication complete as a result of the connections 29 with the segments 14. If necessary, some of the integrated circuits described can be combined into a single one.

The arrangement which has just been described makes it possible to realize the manufacture of cells or of groups of cells provided with electronic decoding circuits and indicating in pairs either the seconds, or the minutes, or the hours, or, in abbreviation, the days of the week, the names of the months or else the day of the month.

The diagram of FIG. 3 shows another form of design. It shows cells 21 to 26 which represent the hours, minutes and seconds of a time indication. Each one of these cells is composed of 20 display elements 27 each one of which has an electroluminescent diode with a gallium arsenide base. The diodes 27 are supported and interconnected by a socket built into the cell and made in the form of an integrated circuit. As can be seen from the drawing, each cell has five rows of four diodes. However, in other forms of design there could be a different number of diodes comprising each cell. This number should be sufficiently large to permit representation of the shape of the figures from 0 to 9 by means of a part of the diodes which have become luminescent, but it should not be too large in order to keep the device under acceptable dimensions. It is possible to make cells of this kind including about 25 cells in surface dimensions of 7 X 3 mm.

It is a known fact that electroluminescent diodes have the property of becoming luminescent under the effect of the passage of a current. it is therefore possible through an appropriate commutation to form the figures 0 to 9 on each cell. The various connections necessary for obtaining each figure on a cell can be established by means of electronic elements built into the integrated circuit supporting the diodes of the cell and the circuit diagram can be such that each pulse supplied to the input changes the diagram of the connections in order to make the next figure appear on the cell. The circuits can also be made so that only the figures 0 to 5 appear successively and that the cell represents 0 once again after having represented 5 when the next pulse is imparted to it. The cells 23 and 25 are of this latter type, whereas the cells 24 and 26 indicate the figures from to 9.

In the two forms of design described the time instrument has, for controlling the cells, a time base generator BT supplying pulses at an appropriate frequency. This time base generator can be of any type, for example quartz, a tuning fork, or, if necessary, a pendulum and spiral. The pulses which it supplies end up in a primary frequency divider D1 supplying pulses at a frequency of 1 c/sec and the output of which is connected on the one hand to the cell 6 or 26 which marks the seconds and, on the other hand, to the input of a secondary frequency divider D2 containing five stages. The first stage of the secondary frequency divider carries out a division by ten and supplies, every ten seconds, a pulse to the cell (5 or 25) which marks the tens of seconds. The second stage carries out a division by six and supplies to the minutes cell (4 or 24) a pulse every 60 seconds. The third stage once more carries out a division by and drives the cell (3 or 23) in tenths of a minute. The fourth and fifth stages of the secondary frequency divider also control the cells (2, 22) and (1, 21) so as to provide an indication of the hours. The fourth stage of the secondary frequency divider is arranged so that the cell (2 or 22) of the hours returns immediately to zero after having indicated the 3 one out of three times, the other indications of the FIG. 3 being followed by the indication of the FIG. 4, etc., right up to 9.

As a variation this stage of the divider could be arranged so that the cell 22 returns immediately to O at the time of passing onto the 4, if the cell 21 indicates the FIG. 2. Finally, the last stage is connected to the next-to-last stage and arranged so as to indicate successively 0, 1 and 2, the commutation taking place each time that the cell 22 returns to 0.

We thus obtain an indication of the hours, minutes and seconds over 24 hours.

In variation, the cells 21 to 26 could also indicate the hour over only 12 hours. In this case the dial could inelude an additional cell which could be composed of only one or a few diodes rendered luminescent from 12 to 0 hours and kept out of circuit from 0 to 12 hours.

The cells could also indicate the hour in a decimal fraction with four or five significant figures after the decimal point: 23.9999 hours or 23.99999 in TMU (Time Measurement Unit) or else in fractions of a minute 23 hours 59.99 minutes. Such displays are already known.

It has been ascertained that it is possible, in cells such as cells 21 to 26 having dimensions of 3 X 3 mm, to create on each one of these cells, by electroluminescense, sufficiently visible figures to permit easy reading of the time when the cells are imbedded in a fixed dial under a glass in an instrument having the size of a small clock. We thus obtain a time instrument giving very visible indications and having a display device without any moving part.

Other designs can also be provided for the cells 21 to 26. Thus, each display element 27 could comprise a luminescent-gas tube, the tubes of each cell or even of all of the cells being assembled in a single unit containing in its upper part one or several transparent electrodes kept under a constant potential whereas the other electrode of each basic tube is connected to the logic circuit so as to receive a pulse at the desired moment.

The various forms of design described above make it possible to create a timepiece with digital display and the dial of which comprises, with the electronic circuit arranged on the other side, a compact unit in which it suffices to connect the input or inputs to the frequency divider of the time base. Particularly if liquid-crystal display cells are used it is possible to make this unit of a size which permits its incorporation into a wrist watch. The dial can be mounted interchangeably in the inside of the case so that after the latter is opened it is possible to separate it easily from the rest of the electronics. Furthermore, the electronic logic only has a small number of inputs connected to the frequency divider.

What is claimed is:

l. A timepiece with digital display composed of a visible panel provided with display cells each one of which is formed of a group of fixed display elements which are capable of changing their optical properties when excited by an electrical pulse, an electronic logic circuit, the outputs of which are connected to the display elements in order to transmit these pulses to them, a time base controlling the electronic logic circuit, and a power source, all being arranged in such a manner that at each moment the indication of the time formed by the cells occurs as a result of the excitation of various sub-assemblies of their elements, characterized by the fact that at least a part of the electronic logic circuit is connected to the panel so that the latter constitutes a monolithic unit provided with the display elements and a minimum number of input connections linking the output of the time base to the electronic logic which is built into the panel, the latter being connected in a detachable manner to the timepiece, wherein the time indication includes at least the hours, the minutes and the days of the week and is composed of cells containing seven elongated display elements arranged so as to show the figures 0 to 9 and of cells containing fourteen elongated display elements arranged so as to indicate the letters of the alphabet.

2. Timepiece according to claim 1 wherein said time indication further includes means indicating the day of the week and the name of the month, characterized in that the cells indicating the day of the month, the day of the week and the name of the month are grouped in pairs, the display elements of each pair of cells being controlled by the same element of integrated circuit connected to the frequency divider.

3. Timepiece according to claim 1, characterized in that the cells with 14 display elements are grouped in pairs, each pair having an integrated electronic circuit on the other side providing the decoding from successive pulses received at an input connection so as to form at each pulse two letters of at least one of the successive days of the week and one of the months of the year.

4. A timepiece, with digital display, comprising: a case; a panel removably located within said case and having a front side and a rear side; at least six display cells located within said panel, each comprising a plurality of fixed display elements changing their optical properties when excited by an electrical pulse, said cells being arranged to form a time indication comprising at least the seconds, the minutes and the hours; an electronic logic circuit fixedly mounted within said panel; means permanently connecting said logic circuit to said display elements; input connections fixedly mounted into said panel and projecting at the rear side thereof; said input connections being connected to said logic circuit; a power source; a time standard; and means detachably connecting said time standard and said power source to said input connections.

5. A timepiece according to claim 4, wherein the number of said input connections is three.

6. A timepiece with digital display, comprising: a case; a panel having front and rear faces removably located within said case; display cells located within said panel for indicating time, each comprising at least one fixed display element changing its optical properties when excited by an electrical pulse; an electronic logic circuit fixedly mounted within said panel, said circuit being connected to the display elements of a given number of said cells; input connections fixedly mounted into said panel and projecting at the rear face thereof, said input connections being connected to said logic circuit; a power source and a timebase for controlling said logic circuit located within said case; means electrically connecting said power source and said time base to said input connections; and connecting means between at least a part of said input connections and further display elements comprising other cells than said given number of cells wherein said other cells are continuously excited and show an unchanging indication.

t i i i 

1. A timepiece with digital display composed of a visible panel provided with display cells each one of which is formed of a group of fixed display elements which are capable of changing their optical properties when excited by an electrical pulse, an electronic logic circuit, the outputs of which are connected to the display elements in order to transmit these pulses to them, a time base controlling the electronic logic circuit, and a power source, all being arranged in such a manner that at each moment the indication of the time formed by the cells occurs as a result of the excitation of various sub-assemblies of their elements, characterized by the fact that at least a pArt of the electronic logic circuit is connected to the panel so that the latter constitutes a monolithic unit provided with the display elements and a minimum number of input connections linking the output of the time base to the electronic logic which is built into the panel, the latter being connected in a detachable manner to the timepiece, wherein the time indication includes at least the hours, the minutes and the days of the week and is composed of cells containing seven elongated display elements arranged so as to show the figures 0 to 9 and of cells containing fourteen elongated display elements arranged so as to indicate the letters of the alphabet.
 2. Timepiece according to claim 1 wherein said time indication further includes means indicating the day of the week and the name of the month, characterized in that the cells indicating the day of the month, the day of the week and the name of the month are grouped in pairs, the display elements of each pair of cells being controlled by the same element of integrated circuit connected to the frequency divider.
 3. Timepiece according to claim 1, characterized in that the cells with 14 display elements are grouped in pairs, each pair having an integrated electronic circuit on the other side providing the decoding from successive pulses received at an input connection so as to form at each pulse two letters of at least one of the successive days of the week and one of the months of the year.
 4. A timepiece, with digital display, comprising: a case; a panel removably located within said case and having a front side and a rear side; at least six display cells located within said panel, each comprising a plurality of fixed display elements changing their optical properties when excited by an electrical pulse, said cells being arranged to form a time indication comprising at least the seconds, the minutes and the hours; an electronic logic circuit fixedly mounted within said panel; means permanently connecting said logic circuit to said display elements; input connections fixedly mounted into said panel and projecting at the rear side thereof; said input connections being connected to said logic circuit; a power source; a time standard; and means detachably connecting said time standard and said power source to said input connections.
 5. A timepiece according to claim 4, wherein the number of said input connections is three.
 6. A timepiece with digital display, comprising: a case; a panel having front and rear faces removably located within said case; display cells located within said panel for indicating time, each comprising at least one fixed display element changing its optical properties when excited by an electrical pulse; an electronic logic circuit fixedly mounted within said panel, said circuit being connected to the display elements of a given number of said cells; input connections fixedly mounted into said panel and projecting at the rear face thereof, said input connections being connected to said logic circuit; a power source and a timebase for controlling said logic circuit located within said case; means electrically connecting said power source and said time base to said input connections; and connecting means between at least a part of said input connections and further display elements comprising other cells than said given number of cells wherein said other cells are continuously excited and show an unchanging indication. 